1. Field of the Invention
The present invention generally relates to plumbing devices and, more particularly, to an improved device for temporarily plugging drain pipes in order to test the same.
2. Prior Art
When a new home, condominium or apartment house or the like is constructed, the drains must be tested for leaks before they can be approved by an inspector. This is usually accomplished by first inserting a temporary plug device through the clean-out pipe located outside the structure to a point where it intersects a sewer line running from the structure drain to the main sewer line. Such plug device usually is an elongated hollow expansible sausage-like unit which has a nipple at one end through which air is introduced into the unit until the unit expands sufficiently so that one end blocks the clean-out pipe while the other end of the device seals off the sewer line. Water can then be introduced into the entire house drain and sewer system to check for leaks.
Such a conventional plug device has several drawbacks. Thus, the device is usually difficult to slide into place and to retrieve due to its shape. Moreover, when the device is deflated the fluid from the house drains not only flows into the sewer line but also backs up through the clean-out pipe, especially in multi-story structures, creating a sanitation hazard. Moreover, the device usually is adapted for use only with one diameter of pipes, necessitating various different sizes of the device to use in various plumbing systems. In addition, if the device is subjected to excess pressure during use, it will rupture, with possible serious injury to workmen and the plumbing and sewage system.
Accordingly, there is a need for an improved type of drain pipe plug device which can be inflated with either a liquid or a gas, and is safe to use. Such device should be easy to insert and retrieve, should not rupture even when subjected to excess inflation pressure, and should be adaptable to various drain pipe diameters. Of more importance, the device should prevent, upon its deflation after the drain test is run, back-flow of fluid from the house drains into the clean-out pipe.
An improved form of drain pipe plug device is described and claimed in U.S. Pat. No. 4,660,603 which issued to the inventor of the present application. That device has the above described features locking in other devices. It comprises an expandible tube having a narrow flexible middle portion and larger flexible opposite end portions with an anti-back flow pressure relief valve at the outlet end. In one embodiment, the sidewall thickness of the device is uniform throughout all three portions, while the diameter varies from portion to portion. In another embodiment, each of the three portions has a uniform but separate wall thickness.
It has been found that the device of U.S. Pat. No. 4,660,603 is difficult and expensive to manufacture and does not provide an optimal seal throughout. Accordingly, there remains a need for an improved device which is inexpensive and simple to manufacture and provides optimal drain sealing throughout the device.